Vector signal analyzer: Difference between revisions

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A '''vector signal analyzer''' is an instrument that measures the magnitude and phase of the input signal at a single frequency within the [[Intermediate frequency|IF]] [[Bandwidth (signal processing)|bandwidth]] of the instrument. The primary use is to make in-channel measurements, such as [[error vector magnitude]], code ___domain power, and [[spectral flatness]], on known signals.

Vector signal analyzers are useful in measuring and [[Demodulation|demodulating]] [[Modulation#Digital modulation methods|digitally modulated signals]] like [[W-CDMA (UMTS)|W-CDMA]], [[3GPP Long Term Evolution|LTE]], and [[Wireless LAN|WLAN]].<ref>National Institute of TechnologyStandards and StandardsTechnology [http://www.eeel.nist.gov/kate_papers/R13_NIST_TN1546_Modulated_Signal_(Web)1.pdf], ''Measurement to Support Modulated-Signal Radio Transmissions for the Public-Safety Sector'', p. 15, April, 2008, accessed July 19, 2011.</ref> These measurements are used to determine the quality of [[modulation]] and can be used for design validation and compliance testing of electronic devices.

==Operation==

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===DSP and display stage===

Once the signal is digitized, it is separated into [[quadrature phase|quadrature]] and in-phase components ([[I/Q data]]) using a quadrature detector, which is typically {{cn|date=February 2024}} implemented with a [[Hilbert transform#Discrete Hilbert transform|discrete Hilbert transform]]. Several measurements are made and displayed using these signal components and various [[digital signal processing|DSP]] processes, such as the ones below.

==== Signal spectrum from FFT ====

{{main|Fast Fourier transform}}

A [[fast fourierFourier transform|FFT]] is used to compute the frequency spectrum of the signal. Usually there is a [[window function|windowing function]] option to limit [[spectral leakage]] and enhance frequency resolution.<ref>Keysight [https://stgwww.keysight.com/cn/zh/assets/7018-02679/technical-overviews/5990-6405.pdf], ''Keysight Vector Signal Analysis Basics'', PublishPublished September 30, 2019.</ref> This window is implemented by multiplying it with the digitized values of the sample period before computing the FFT.

==== Constellation diagram ====

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==References==

* [httphttps://www.ewh.ieee.org/r2/baltimore/Chapter/Comm/VSA_COMSOC.pdf Communications Systems Analysis Using Hardware and Software-Based Vector Signal Analyzers]

===Footnotes===